Metamaterial phased array for hyperthermia therapy

ABSTRACT

A device includes a phase shifting element array comprising a plurality of metamaterial structures that resonate in response to an input electromagnetic (EM) signal. The phase shifting element array generates an output EM signal that is a sum of component output electromagnetic signals generated respectively by the metamaterial structures and is configured to propagate wirelessly through at least a portion of a patient&#39;s body. A control circuit controls one or both of phases and amplitudes of the component electromagnetic output signals so that at least one of constructive and destructive interference between the component output electromagnetic signals causes the output signal to have a higher intensity EM radiation at a target region interior to the body and to have a zero or low intensity radiation at a non-target region interior to the body.

TECHNICAL FIELD

This disclosure relates generally to hyperthermia therapy systems andmethods pertaining to such systems.

BACKGROUND

Hyperthermia therapy is a type of medical treatment in which body tissueis exposed to slightly higher temperatures (e.g. greater than about 100F) to damage and kill cancer cells. Hyperthermia therapy helps makecancer cells more vulnerable to the effects of other treatments, likeradiation therapy and certain chemotherapy drugs. Hyperthermia therapyis a promising treatment option for patients with advanced or recurrentcancer.

SUMMARY

Some embodiments are directed to a device having a phase shiftingelement array including a plurality of metamaterial structures thatresonate in response to an input electromagnetic (EM) signal. The phaseshifting element array generates an output EM signal that is a sum ofcomponent output electromagnetic signals generated respectively by themetamaterial structures and is configured to propagate wirelesslythrough at least a portion of a patient's body. The device includes acontrol circuit configured to control one or both of phases andamplitudes of the component electromagnetic output signals so that atleast one of constructive and destructive interference between thecomponent output electromagnetic signals causes the output signal tohave a higher intensity EM radiation at a target region interior to thebody and to have a zero or low intensity radiation at a non-targetregion interior to the body. The higher intensity EM radiation generatesa tissue temperature suitable for hyperthermia therapy at the targetregion. For example, the tissue temperature at the target region may bein in range of about 40 C to 50 C. The control circuit can be configuredto control at least one of position, focus, and intensity of the higherintensity EM radiation at the target region.

According to some aspects, the control circuit includes variablecapacitors electrically coupled respectively to the metamaterialstructures so that a change in capacitance of one of the variablecapacitors changes a phase of a component output signal of an associatedmetamaterial structure. The control circuit includes a signal generatorconfigured to generate control signals that control capacitances of thevariable capacitors. The input EM signal may propagate to the array ofmetamaterial structures through a wire probe antenna and/or through awaveguide.

According to some aspects, each metamaterial structure includes a firstmetal layer structure, an electrically isolated second metal layerstructure, and a dielectric layer disposed between the first and secondmetal structures. The first and second metal layer structures arecooperatively configured such that the metamaterial structure resonatesat a frequency of the input EM signal at a fixed capacitance. The firstmetal layer structure may be disposed on an upper dielectric surface ofthe dielectric layer. The metamaterial structure may further include athird metal layer structure disposed on the upper dielectric surface andspaced apart from the first metal layer structure. A variable capacitorhas a first terminal electrically coupled to the first metal layerstructure and a second terminal electrically coupled to the third metallayer structure.

In some embodiments, the first metal layer structure is disposed on anupper dielectric surface of the dielectric layer. The metamaterialstructure further comprises a third metal layer structure disposed onthe upper dielectric surface and spaced apart from the first metal layerstructure. A second metamaterial structure comprises a fourth metallayer structure disposed on a lower dielectric surface and is spacedapart from the second metal layer structure. A second variable capacitorhas a first terminal electrically coupled to the second metal layerstructure and a second terminal electrically coupled to the fourth metallayer structure. For example, the metamaterial structure on the upperdielectric surface may be a mirror image of the metamaterial structureon the lower dielectric surface.

According to some embodiments, the first metal layer structure comprisesa patterned planar structure defining one or more open regions. Forexample, the first metal layer structure can include a peripheral frameportion including an outer peripheral edge, one or more radial arms,each radial arm having a first end integrally connected to theperipheral frame portion and extending inward from the peripheral frameportion toward a central region of the metamaterial structure, and aninner structure integrally connected to second ends of the one or moreradial arms, the inner structure being spaced from the peripheral frameportion.

In some configurations, the control signal is configured to control thecomponent EM output signals to scan the output signal across a detectionarea. The control circuit may be configured to generate beam directiondata indicating instantaneous scan direction of the output signal. Thedevice can include a detector circuit configured to detect a portion ofthe output signal reflected from a structure interior to the body and asignal processing circuit configured to combine the scan direction andthe reflected portion of the output signal and to provide informationabout the structure. For example, the information may comprise one ormore of presence, size, location, and image information.

Some embodiments are directed to a method or providing therapy. Anoutput EM signal is generated that is a sum of component outputelectromagnetic signals generated respectively by a plurality ofmetamaterial structures that resonate in response to an inputelectromagnetic (EM) signal. The output EM is propagated wirelesslythrough at least a portion of a patient's body. One or both of phasesand amplitudes of the component electromagnetic output signals arecontrolled so that at least one of constructive and destructiveinterference between the component output electromagnetic signals causesthe output signal to have a higher intensity EM radiation at a targetregion interior to the body and to have a zero or low intensityradiation at a non-target region interior to the body. The higherintensity electromagnetic radiation generates a tissue temperaturesuitable for hyperthermia therapy at the target region.

In some embodiments the method further includes controlling thecomponent electromagnetic output signals to scan the output signalacross a detection area. Beam direction data is generated that indicatesinstantaneous scan direction of the output signal. A portion of theoutput signal reflected from a structure interior to the body isdetected. The scan direction and the reflected portion of the outputsignal are combined to provide information about the structure.

According to some embodiments, a device includes a phase shiftingelement array comprising a plurality of metamaterial structures thatresonate in response to an input electromagnetic (EM) signal. The phaseshifting element array generates an output EM signal that is a sum ofcomponent output electromagnetic signals generated respectively by themetamaterial structures. The output EM signal is configured to propagatewirelessly through at least a portion of a patient's body. A controlcircuit is configured to control one or both of phases and amplitudes ofthe component electromagnetic output signals so that at least one ofconstructive and destructive interference between the component outputelectromagnetic signals causes the output signal to scan the outputsignal across a detection area. The control circuit generates beamdirection data indicating instantaneous scan direction of the outputsignal. A detector circuit detects a portion of the output signalreflected from a structure interior to the body. A signal processingcircuit combines the scan direction and the reflected portion of theoutput signal and to provide information about the structure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a block diagram of a system in accordance with someembodiments;

FIG. 1B shows a therapy system in accordance with various embodimentsthat is in use;

FIG. 1C is a simplified side view showing a phase shifting apparatusaccording to a generalized embodiment of the present invention;

FIG. 2 is a diagram showing exemplary phase shifting characteristicsassociated with operation of the phase shifting apparatus of FIG. 1;

FIGS. 3A and 3B are exploded perspective and assembled perspectiveviews, respectively, showing a phase shifting element according to anexemplary embodiment;

FIG. 3C is an exploded and assembled perspective view showing a phaseshifting element that includes first and second metamaterial structuresaccording to an exemplary embodiment;

FIG. 4 is a cross-sectional side view showing a phase shifting apparatusincluding the phase shifting element of FIG. 3B according to anotherexemplary embodiment;

FIG. 5 is a perspective view showing a phase shifting element includingan exemplary patterned metamaterial structure according to anotherembodiment;

FIG. 6 is a cross-sectional side view showing a simplified phased arraysystem including four phase shifting elements according to anotherexemplary embodiment;

FIG. 7 is a simplified perspective view showing a phase shifting elementarray according to another exemplary embodiment;

FIG. 8 is a simplified diagram depicting a phased array system includingthe phase shifting element array of FIG. 7 according to anotherembodiment;

FIG. 9 is simplified diagram showing a phased array system includingmetamaterial structures disposed in a two-dimensional pattern accordingto another exemplary embodiment; and

FIGS. 10A, 10B and 10C are diagrams depicting emitted beams generated invarious exemplary directions by the phased array system of FIG. 9.

FIGS. 10D, 10E, 10F, and 10G provide modeling data that demonstratesfocusing the local hyperthermia beam in x, y, and depth (into the body)dimensions;

FIG. 11 is a block diagram of an imaging system in accordance with someembodiments; and

FIG. 12 is a simplified side view showing an imaging system according tosome embodiments.

The figures are not necessarily to scale. Like numbers used in thefigures refer to like components. However, it will be understood thatthe use of a number to refer to a component in a given figure is notintended to limit the component in another figure labeled with the samenumber.

DETAILED DESCRIPTION

Embodiments described herein involve a treatment and/or imaging systemuseful for tumor treatment and/or detection. The system is based on aphase shifting array that selectively provides electromagnetic radiationto a target region within the patient's body. The phase shifting arrayincludes a plurality of metamaterial structures that resonate inresponse to an input electromagnetic (EM) signal. The phase shiftingelement array generates an output EM signal that is the combination ofcomponent output electromagnetic signals generated respectively by eachof the metamaterial structures. The output signal is configured topropagate wirelessly through at least a portion of a patient's body. Acontrol circuit controls one or both of phases and amplitudes of thecomponent electromagnetic output signals so that at least one ofconstructive and destructive interference between the component outputelectromagnetic signals causes the output signal to have a higherintensity EM radiation at a target region interior to the body and tohave a zero or low intensity radiation at a non-target region interiorto the body. The higher intensity EM radiation generates a specifiedamount of heat flux the target region, thus providing noninvasivehyperthermia treatment within the patient's body.

According to some aspects, the system may be configured to control thephases of the respective component output signals so that the outputsignal can be caused to scan or “sweep” an area or region into which theoutput signal is directed. The control circuit generates scan directiondata that includes the instantaneous scan direction of the outputsignal. The system includes a receiver circuit configured to detect aportion of the output signal that is reflected from one or morestructures interior to the body. Signal processing circuit combines thescan direction and the detected portion of the output signal to provideinformation about presence and location of the structures.

FIG. 1A is a schematic diagram of a system 160 in accordance with someembodiments. FIG. 1A depicts an input source 161 that provides an inputelectromagnetic (EM) radiation signal to a phase shifting array 162. Acontrol circuit 163 is coupled to control the phase shifting array 162and is optionally coupled to control the input source. According tovarious implementations, the control circuit 163 may be capable ofcontrolling one or more of the phase of each component output signal,the amplitude of each component output signal, the frequency of theinput signal and the amplitude of the input signal. The input source 161includes a signal generator 161 a such as an oscillator, coupled to apower amplifier 161 b that boosts the input signal. According to someimplementations, the input source 161 may produce a continuous wave (CW)voltage oscillating sinusoidally at a specified microwave frequency,e.g., 3 kHz to 300 GHz or in some implementations about 915 MHz. Theinput signal can be transmitted to the phase shifting array through anantenna and/or waveguide 161 c, e.g., a wire probe antenna disposedwithin a metal waveguide structure that causes the input signal to beincident on the phased array as described in more detail below. Thephased array 162 is configured to provide beam shaping and beam formingof the output signal beam due to constructive and/or destructiveinterference between the component output electromagnetic signals. Thebeam forming/beam shaping causes the output beam 166 a to have a higherintensity EM radiation at a target region 164 a interior to thepatient's body 164 and to have a zero or low intensity radiation at anon-target region 164 b interior to the patient's body 164. The higherintensity EM radiation can be controlled to a specified amount of heatflux the target region 164 a to provide noninvasive hyperthermiatreatment within the patient's body.

In some scenarios, multiple phased arrays 162 a, 162 b may be used toproduce multiple output beams 166 a, 166 b. Optionally, in someembodiments, a first output signal beam 166 a may be substantiallyorthogonal to a second output signal beam 166 b. FIG. 1B shows a phasedarray 162 positioned relative to a patient with control lines 163 a andwaveguides 161 c visible.

FIG. 1C is a simplified side view showing a system 200 including atleast one metamaterial-based phase shifting element 100 according to ageneralized exemplary embodiment. Phase shifting element 100 utilizes ametamaterial structure 140 to produce an output signal S_(OUT) havingthe same radio wave frequency as that of an applied/received inputsignal S_(IN), and utilizes a variable capacitor 150 to control a phasep_(OUT) of output signal S_(OUT) by way of an applied phase controlsignal (e.g., either an externally supplied digital signal C or adirect-current control voltage Vc). System 200 also includes a portionof a signal source 205 (e.g., a feed horn or a leaky-wave feed) disposedin close proximity to phase shifting element 100 and configured togenerate input signal S_(IN) at a particular radio wave frequency (e.g.,in the range of 3 kHz to 300 GHz) and an input phase p_(IN), where theradio wave frequency matches resonance characteristics of phase shiftingelement 100, and a control circuit 210 (e.g., including adigital-to-analog converter (DAC) that is controlled by any of a fieldprogrammable gate array (FPGA), an application specific integratedcircuit (ASIC, or a micro-processor) that is configured to generatephase control voltages Vc applied to variable capacitor 150 at voltagelevels determined in accordance with (e.g., directly or indirectlyproportional to) a pre-programmed signal generation scheme or anexternally supplied phase control signal C.

Metamaterial structure 140 is preferably a layered metal-dielectriccomposite architecture, but may be engineered in a different form,provided the resulting structure is configured to resonate at the radiofrequency of applied input signal S_(IN), and has a large phase swingnear resonance such that metamaterial structure 140 generates outputsignal S_(OUT) at the input signal frequency by retransmitting (e.g.,reflecting/scattering) input signal S_(IN). In providing this resonance,metamaterial structure 140 is produced with an inherent “fixed”capacitance C_(M) and an associated inductance that collectively providethe desired resonance characteristics. As understood in the art, theterm “metamaterial” identifies an artificially engineered structureformed by two or more materials and multiple elements that collectivelygenerate desired electromagnetic properties, where metamaterial achievesthe desired properties not from its composition, but from theexactingly-designed configuration (e.g., the precise shape, geometry,size, orientation and arrangement) of the structural elements formed bythe materials. As used herein, the phrase “metamaterial structure” isintended to mean a dynamically reconfigurable/tunable metamaterialhaving radio frequency resonance and large phase swing propertiessuitable for the purpose set forth herein. The resulting structureaffects radio frequency (electromagnetic radiation) waves in anunconventional manner, creating material properties which areunachievable with conventional materials. Metamaterial structuresachieve their desired effects by incorporating structural elements ofsub-wavelength sizes (having a period of λ/2 or less), e.g. featuresthat are actually smaller than the radio frequency wavelength of thewaves they affect. In the practical embodiments described below,metamaterial structure 140 is constructed using inexpensive metal filmor PCB fabrication technology that is tailored by solving Maxwell'sequations to resonate at the radio frequency of applied input signalS_(IN), whereby the metamaterial structure 140 generates output signalS_(OUT) at the input signal frequency by retransmitting (e.g.,reflecting/scattering) the input signal S_(IN).

Variable capacitor 150 is connected between metamaterial structure 140and ground (or other fixed direct-current (DC) voltage supply). Asunderstood in the art, variable capacitors are typically two-terminalelectronic devices configured to produce a capacitance that isintentionally and repeatedly changeable by way of an applied electroniccontrol signal. In this case, variable capacitor 150 is coupled tometamaterial structure 140 such that an effective capacitance C_(eff) ofmetamaterial structure 140 is determined by a product of inherentcapacitance C_(M) and a variable capacitance C_(V) supplied by variablecapacitor 150. The output phase of metamaterial structure 140 isdetermined in part by effective capacitance C_(eff), so output phasep_(OUT) of output signal S_(OUT) is “tunable” (adjustably controllable)to a desired phase value by way of changing variable capacitance C_(V),and this is achieved by way of changing the phase control signal (e.g.,digital control signal C and/or DC bias voltage Vc) applied to variablecapacitor 150.

FIG. 2 is a diagram showing exemplary phase shifting characteristicsassociated with operation of phase shifting apparatus 200. Inparticular, FIG. 2 shows how output phase p_(OUT) of output signalS_(OUT) changes in relation to phase control voltage Vc. Because outputphase p_(OUT) varies in accordance with effective capacitance C_(eff) ofmetamaterial structure 140 which in turn varies in accordance withvariable capacitance C_(V) generated by variable capacitor 150 onmetamaterial structure 140 (shown in FIG. 1C), FIG. 2 also effectivelydepicts operating characteristics of variable capacitor 150 (e.g., FIG.2 effectively illustrates that variable capacitance C_(V) varies inaccordance with phase control voltage Vc by way of showing how outputphase p_(OUT) varies in accordance with phase control voltage Vc). Forexample, when phase control voltage Vc has a voltage level of 6V,variable capacitor 150 generates variable capacitance C_(V) at acorresponding capacitance level (indicated as “C_(V)=C1”) andmetamaterial structure 140 generates output signal S_(OUT) at anassociated output phase p_(OUT) of approximately 185°. When phasecontrol voltage Vc is subsequently increased from 6V to a second voltagelevel (e.g., 8V), variable capacitor 150 generates variable capacitanceat a second capacitance level (indicated as “C_(V)=C2”) such thatmetamaterial structure 140 generates output signal S_(OUT) at anassociated second output phase p_(OUT) of approximately 290°.

Referring again to FIG. 1C, phase control voltage Vc is applied acrossvariable capacitor 150 by way of a conductive structure 145 that isconnected either to metamaterial structure 140 or directly to a terminalof variable capacitor 150. Specifically, variable capacitor 150 includesa first terminal 151 connected to metamaterial structure 140 and asecond terminal 152 connected to ground. As indicated in FIG. 1C,conductive structure 145 is either connected to metamaterial structure140 or to first terminal 151 of variable capacitor 150 such that, whenphase control voltage Vc is applied to conductive structure 145,variable capacitor 150 generates an associated variable capacitanceC_(V) having a capacitance level that varies in accordance with thevoltage level of phase control voltage Vc in the manner illustrated inFIG. 2 (e.g., the capacitance level of variable capacitance C_(V)changes in direct proportion to phase control voltage Vc).

As set forth in the preceding exemplary embodiment, some scenariosinvolve a phase shifting methodology involving control over radio waveoutput signal phase p_(OUT) by selectively adjusting effectivecapacitance C_(eff) of metamaterial structure 140, which is implementedin the exemplary embodiment by way of controlling variable capacitor 150using phase control voltage Vc to generate and apply variablecapacitance C_(V) onto metamaterial structure 140. Although the use ofvariable capacitor 150 represents the presently preferred embodiment forgenerating variable capacitance C_(V), those skilled in the art willrecognize that other circuits may be utilized to generate a variablecapacitance that controls effective capacitance C_(eff) of metamaterialstructure 140 in a manner similar to that described herein. Accordingly,the novel methodology is alternatively described as including: causingmetamaterial structure 140 to resonate at the radio wave frequency ofinput signal S_(IN); applying a variable capacitance C_(V) (e.g., fromany suitable variable capacitance source circuit) to metamaterialstructure 140 such that effective capacitance C_(eff) of metamaterialstructure 140 is altered by variable capacitance C_(V); and adjustingvariable capacitance C_(V) (e.g., by way of controlling the suitablevariable capacitance source circuit) until effective capacitance C_(eff)of metamaterial structure 140 has a capacitance value that causesmetamaterial structure 140 to generate radio frequency output signalS_(OUT) with output phase p_(OUT) set at a desired phase value (e.g.,290°).

As mentioned above, some implementations involve the use of layeredmetamaterial structures. FIGS. 3A and 3B are exploded perspective andassembled perspective views, respectively, showing a phase shiftingelement 100A including a two-terminal variable capacitor 150A and ametamaterial structure 140A having an exemplary three-level embodiment.FIG. 4 shows a phase shifting apparatus 200A including phase shiftingelement 100A in cross-sectional side view. Beneficial features andaspects of the three-layer structure used to form metamaterial structure140A, and their usefulness in forming metamaterial-based phase shiftingelement 100A and apparatus 200A, are described below with reference toFIGS. 3A, 3B and 4.

Referring to FIGS. 3A and 3B three-layer metamaterial structure 140A isformed by an upper/first metal layer (island) structure 141A, anelectrically isolated (e.g., floating) backplane (lower/second metal)layer structure 142A, and a dielectric layer 144A-1 sandwiched betweenupper island structure 141A and backplane layer 142A, where islandstructure 141A and backplane layer 142A are cooperatively tailored(e.g., sized, shaped and spaced by way of dielectric layer 144A-1) suchthat the composite three-layer structure of metamaterial structure 140Ahas an inherent (fixed) capacitance C_(M) that is at least partiallyformed by capacitance C₁₄₁₋₁₄₂ (e.g., the capacitance between islandstructure 141A and backplane layer 142A), and such that metamaterialstructure 140A resonates at a predetermined radio wave frequency (e.g.,2.4 GHz). As discussed above, an effective capacitance of metamaterialstructure 140A is generated as a combination of fixed capacitance C_(M)and an applied variable capacitance, which in this case is applied toisland structure 141A by way of variable capacitor 150A. In thisarrangement, island structure 141A acts as a wavefront reshaper, whichensures that the output signal S_(OUT) is directed in the upwarddirection only (e.g., such that the radio frequency output signal isemitted from island structure 141A in a direction away from backplanelayer 142A), and which minimizes power consumption because of efficientscattering with phase shift.

According to a presently preferred embodiment, dielectric layer 144A-1comprises a lossless dielectric material. For example, in someimplementations, the dielectric material can comprise RT/duroid® 6202Laminates, Polytetrafluoroethylene (PTFE), and TMM4® dielectric, allproduced by Rogers Corporation of Rogers, Conn. The use of such losslessdielectric materials mitigates absorption of incident radiation (e.g.,input signal S_(IN)), and ensures that most of the incident radiationenergy is re-emitted in output signal S_(OUT). An optional lowerdielectric layer 144A-2 is provided to further isolate backplane layer142A, and to facilitate the backside mounting of control circuits in themanner described below.

According to another feature, both island (first metal layer) structure141A and a base (third) metal layer structure 120A are disposed on anupper surface 144A-1A of dielectric layer 141A-1, where base metalstructure 120A is spaced from (e.g., electrically separated by way of agap G) island structure 141A. Metal layer structure 120A is connected toa ground potential during operation, base, whereby base layer structure120A facilitates low-cost mounting of variable capacitor 150A duringmanufacturing. For example, using pick-and-place techniques, variablecapacitor 150A is mounted such that first terminal 151A is connected(e.g., by way of solder or solderless connection techniques) to islandstructure 141A, and such that second terminal 152A is similarlyconnected to base metal structure 120A.

According to some implementations, base metal structure 120A comprises ametal film or PCB fabrication layer that entirely covers upperdielectric surface 144A-1A except for the region defined by an opening123A, which is disposed inside an inner peripheral edge 124A, whereisland structure 141A is disposed inside opening 123A such that an outerperipheral edge 141A-1 of is structure 141A is separated from innerperipheral edge 124A by peripheral gap G, which has a fixed gap distancearound the entire periphery. By providing base metal structure 120A suchthat it substantially covers all portions of upper dielectric surface144A-1A not occupied by island structure 141A, base metal layer 120Aforms a scattering surface that supports collective mode oscillations,and ensures scattering of the wave in the forward direction. Inaddition, island structure 141A, backplane layer 142A and base metalstructure 120A are cooperatively configured (e.g., sized, shaped andspaced) such that inherent (fixed) capacitance C_(M) includes both theisland-backplane component C₁₄₁₋₁₄₂ and an island-base componentC₁₄₁₋₁₂₀, and such that metamaterial structure 140A resonates at thedesired radio wave frequency. In this way, base metal layer 120Aprovides the further purpose of effectively forming part of metamaterialstructure 140A by enhancing fixed capacitance C_(M).

According to another feature, both base (third) metal layer structure120A and island (first metal layer) structure 141A comprise a singlemetal (e.g., both base metal structure 120A and island structure 141Acomprise the same, identical metal composition, e.g., copper). Thissingle-metal feature facilitates the use of low-cost manufacturingtechniques in which a single metal film or PCB fabrication is depositedon upper dielectric layer 144A-1A, and then etched to define peripheralgap G. In other embodiments, different metals may be patterned to formthe different structures.

According to another feature shown in FIG. 3A, a metal via structure145A is formed using conventional techniques such that it extendsthrough lower dielectric layer 144A-2, through an opening 143A definedin backplane layer 142A, through upper dielectric layer 144A-1, andthrough an optional hole H formed in island structure 141A to contactfirst terminal 151A of variable capacitor 150A. This via structureapproach facilitates applying phase control voltages to variablecapacitor 150A without significantly affecting the electricalcharacteristics of metamaterial structure 140A. As set forth below, thisapproach also simplifies the task of distributing multiple controlsignals to multiple metamaterial structures forming a phased array.

FIG. 4 is a cross-sectional side view showing a phase shifting apparatus200A generating output signal S_(OUT) at an output phase p_(OUT)determined an externally-supplied phase control signal C. Apparatus 200Aincludes a signal source 205A, phase shifting element 100A, and acontrol circuit 210A. Signal source 205A includes a suitable signalgenerator (e.g., a feed horn) that generates an input signal S_(IN) at aspecific radio wave frequency (e.g., 2.4 GHz), and is positioned suchthat input signal S_(IN) is directed onto phase shifting element 100A,which is constructed as described above to resonate at the specificradio wave frequency (e.g., 2.4 GHz) such that it generates an outputsignal S_(OUT). Control circuit 210A is configured to generate a phasecontrol voltage Vc in response to phase control signal C such that phasecontrol voltage Vc changes in response to changes in phase controlsignal C. Phase control voltage Vc is transmitted to variable capacitor150A, causing variable capacitor 150A to generate and apply acorresponding variable capacitance onto island structure 141A, wherebymetamaterial structure 140A is caused to generate output signal S_(OUT)at an output phase p_(OUT) determined by phase control signal C. Notethat control circuit 210A is mounted below dielectric layer 144A-2(e.g., below backplane layer 142A), and phase control voltage Vc istransmitted by way of conductive via structure via 145A to terminal 151Aof variable capacitor 150A.

Those skilled in the art understand that the metamaterial structuresgenerally described herein can take many forms and shapes, provided theresulting structure resonates at a required radio wave frequency, andhas a large phase swing near resonance. The embodiment shown in FIGS.3A, 3B and 4 utilizes a simplified square-shaped metamaterial structureand a solid island structure 141A to illustrate basic concepts accordingto some embodiments. Specifically, metamaterial structure 140A is formedsuch that inner peripheral edge 124A surrounding opening 123A in basemetal structure 120A and outer peripheral edge 141A-1 of islandstructure 141A comprise concentric square shapes such that a width ofperipheral gap G remains substantially constant around the entireperimeter of island structure 141A. The use of square-shaped structuresmay simplify the geometric construction and provide limited degrees offreedom that simplify the mathematics needed to correlate phase controlvoltage Vc with desired capacitance change and associated phase shift.In alternative embodiments, metamaterial structures are formed usingshapes other than squares (e.g., round, triangular, rectangular/oblong).

FIG. 3C shows a phase shifting element 100F that includes a firstmetamaterial structure 140F, a second metamaterial structure 140F′, anda two-terminal variable capacitor 150F′. In some embodiments, the secondmetamaterial structure 140F′ is a mirror image of the first metamaterialstructure 140F. The metal structure at the top of FIG. 3C (elements 120Fand 141F) is the same or similar to the metal structure at the top ofFIG. 3C (elements 142F and 141F′). The first and second metamaterialstructures may comprise patterned layers, e.g., as depicted in FIG. 5.

First metamaterial structure 140F is formed by an upper/first metallayer (island) structure 141F, a second metal layer structure 142F, anda dielectric layer 144F sandwiched between the first metal layer(island) structure 141F and second metal layer 142F.

Second metamaterial structure 140F′ is formed by an lower/fourth metallayer (island) structure 141F′, a third metal layer structure 120F, andthe dielectric layer 144F sandwiched between the fourth metal layer(island) structure 141F′ and third metal layer structure 120F. The firstand second metamaterial structures are cooperatively tailored (e.g.,sized, shaped and spaced by way of dielectric layer 144F) such that themetamaterial structures 140F, 140F′ have an inherent (fixed) capacitancethat enables the first and second metamaterial structures 140F, 140F′ toresonate at a predetermined radio wave frequency. An effectivecapacitance of metamaterial structures 140F, 140F′ is generated as acombination of fixed capacitances and applied variable capacitances,which in this case is applied to island structure 141F and/or 141F′ byway of variable capacitor 150F′.

Both the first metal layer (island) structure 141F and the third metallayer structure 120F are disposed on an upper surface 144F-1 ofdielectric layer 144F, where the third metal layer structure 120F isspaced from (e.g., electrically separated by way of a gap) first metallayer (island) structure 141F. Third metal layer structure 120F may beconnected to a ground potential during operation.

Both the fourth metal layer (island) structure 141F′ and a second metallayer structure 142F are disposed on a lower surface 144F-2 ofdielectric layer 144F, where second metal layer structure 142F is spacedfrom (e.g., electrically separated by way of a gap) fourth metal layer(island) structure 141F′. Second metal layer structure 142F may beconnected to a ground potential during operation. Variable capacitor150F′ is mounted such that the first terminal of variable capacitor150F′ is connected (e.g., by way of solder or solderless connectiontechniques) to fourth metal layer (island) structure 141F′, and thesecond terminal of variable capacitor 150F′ is similarly connected tothe second metal layer structure 142F.

FIG. 5 is a top view showing a phase shifting element 100B including anexemplary patterned metamaterial structure 140B according to anexemplary specific embodiment. In this embodiment, island structure 141Bis formed as a patterned planar structure that defines open regions 149B(e.g., such that portions of upper dielectric surface 144B-1A areexposed through the open regions). In this example, island structure141B includes a square-shaped peripheral frame portion 146B including anouter peripheral edge 141B-1 that is separated by a peripheral gap Gfrom an inner peripheral edge 124B of base metal layer portion 120B,which is formed as described above, four radial arms 147B having outerends integrally connected to peripheral frame portion 146B and extendinginward from frame portion 146B, and an inner (in this case, “X-shaped”)structure 148B that is connected to inner ends of radial arms 147B.Structure 148B extends into open regions 149B, which are formed betweenradial arms 147B and peripheral frame 146B. Metamaterial structure 140Bis otherwise understood to be constructed using the three-layer approachdescribed above with reference to FIGS. 3A, 3B and 4. Although the useof patterned metamaterial structures may complicate the mathematicsassociated with correlating control voltage and phase shift values, theX-shaped pattern utilized by metamaterial structure 140B is presentlybelieved to produce more degrees of freedom than is possible using solidisland structures, leading to close to 360° phase swings, which in turnenables advanced functions such as beam steering at large angles (e.g.,greater than plus or minus 60°). In addition, although metamaterialstructure 140B is shown as having a square-shaped outer peripheral edge,patterned metamaterial structures having other peripheral shapes mayalso be beneficially utilized.

FIG. 6 is a cross-sectional side view showing a simplifiedmetamaterial-based phased array system 300C for generating an emittedradio frequency energy beam B in accordance with another embodiment.Phased array system 300C generally includes a signal source 305C, aphase shifting element array 100C, and a control circuit 310C. Signalsource 305C is constructed and operates in the manner described abovewith reference to apparatus 200A to generate an input signal S_(IN)having a specified radio wave frequency and an associated input phasep_(IN).

According to some aspects, phase shifting element array 100C includesmultiple (in this case four) metamaterial structures 140C-1 to 140C-4that are disposed in a predetermined coordinated pattern, where each ofthe metamaterial structures is configured in the manner described aboveto resonate at the radio wave frequency of input signal S_(IN) in orderto respectively produce output signals S_(OUT1) to S_(OUT4). Forexample, metamaterial structure 140C-1 fixed capacitance C_(M1)and isotherwise configured to resonate at the radio wave frequency of inputsignal S_(IN) in order to produce output signal S_(OUT1). Similarly,metamaterial structure 140C-2 has fixed capacitance C_(M2), metamaterialstructure 140C-3 has fixed capacitance C_(M3), and metamaterialstructure 140C-4 has fixed capacitance C_(M4), where metamaterialstructures 140C-2 to 140C-4 are also otherwise configured to resonate atthe radio wave frequency of input signal S_(IN) to produce outputsignals S_(OUT2), S_(OUT3) and S_(OUT4), respectively. The coordinatedpattern formed by metamaterial structures 140C-1 to 140C-4 is selectedsuch that output signals S_(OUT1) to S_(OUT4) combine to produce anelectro-magnetic wave. Although four metamaterial structures areutilized in the exemplary embodiment, this number is arbitrarilyselected for illustrative purposes and brevity, and array 100C may beproduced with any number of metamaterial structures.

Similar to the single element embodiments described above, phaseshifting element array 100C also includes variable capacitors 150C-1 to150C-4 that are coupled to associated metamaterial structures 140C-1 to140C-4 such that effective capacitances C_(eff1) to C_(eff4) ofmetamaterial structures 140C-1 to 140C-4 are respectively alteredcorresponding changes in variable capacitances C_(V1) to C_(V4), whichin turn are generated in accordance with associated applied phasecontrol voltages Vc1 to Vc4. For example, variable capacitor 150C-1 iscoupled to metamaterial structure 140C-1 such that effective capacitanceC_(eff1) is altered by changes in variable capacitance C_(V1), which inturn changes in accordance with applied phase control voltage Vc1.

According to another aspect of the present embodiment, control circuit310C is configured to independently control the respective output phasesp_(OUT1) to p_(OUT4) of output signals S_(OUT1) to S_(OUT4) using apredetermined set of variable capacitances C_(V1) to C_(V4) that arerespectively applied to metamaterial structures 140C-1 to 140C-4 suchthat output signals S_(OUT1) to S_(OUT4) cumulatively generate emittedbeam B in a desired direction. That is, as understood by those skilledin the art, by generating output signals S_(OUT1) to S_(OUT4) with aparticular coordinated set of output phases p_(OUT1) to p_(OUT4), theresulting combined electro-magnetic wave produced by phase shiftingelement array 100C is reinforced in the desired direction and suppressedin undesired directions, thereby producing beam B emitted in the desireddirection from the front of array 100C. By predetermining a combination(set) of output phases p_(OUT1) to p_(OUT4) needed to produce beam B ina particular direction, and by predetermining an associated combinationof phase control voltages Vc1 to Vc4 needed to produce this combinationof output phases p_(OUT1) to p_(OUT4), and by constructing controlcircuit 310C such that the associated combination of phase controlvoltages Vc1 to Vc4 are generated in response to a beam control signalC_(B) having a signal value equal to the desired beam direction,embodiments described herein facilitate the selective generation ofradio frequency beam that are directed in a desired direction. Forexample, as depicted in FIG. 6, in response to a beam control signalC_(B) having a signal value equal to a desired beam direction of 60°,control circuit 310C generates an associated combination of phasecontrol voltages Vc1 to Vc4 that cause metamaterial structures 140C-1 to140C-4 to generate output signals S_(OUT1) to S_(OUT4) at output phasesp_(OUT1) to p_(OUT4) of 468°, 312°, 156° and 0°, respectively, wherebyoutput signals S_(OUT1) to S_(OUT4) cumulatively produce emitted beam Bat the desired 60° angle.

FIG. 7 is a simplified perspective and cross-sectional view showing aphase shifting element array 100D in which metamaterial structures140D-1 to 140D-4 are formed using the three-layered structure describedabove with reference to FIGS. 3A and 3B, and arranged in aone-dimensional array and operably coupled to variable capacitors 150D-1to 150D-4, respectively. Similar to the single element embodimentdescribed above, phase shifting element array 100D includes anelectrically isolated (floating) metal backplane layer 142D, and(lossless) dielectric layers 144D-1 and 144D-2 disposed above and belowbackplane layer 142D.

As indicated in FIG. 7, each metamaterial structure (e.g., structure140D-1) includes a metal island structure 141D-1 disposed on upperdielectric layer 144D-1 and effectively includes an associated backplanelayer portion 142D-1 of backplane layer 142D disposed under metal islandstructure 141D-1 with an associated portion of the dielectric layer144A-1 sandwiched therebetween). For example, metamaterial structure140D-1 includes island structure 141D-1, backplane layer portion 142D-1,and an associated portion of upper dielectric layer 144A-1 that issandwiched therebetween. Similarly, metamaterial structure 140D-2includes island structure 141D-2 and backplane layer portion 142D-2,metamaterial structure 140D-3 includes island structure 141D-3 andbackplane layer portion 142D-3, and metamaterial structure 140D-4includes island structure 141D-4 and backplane layer portion 142D-4.Consistent with the single element description provided above, eachassociated metal island structure and backplane layer portion arecooperatively configured (e.g., sized and spaced) such that eachmetamaterial structure resonates at a specified radio frequency. Forexample, metal island structure 141D-1 and backplane layer portion142D-1 are cooperatively configured to produce a fixed capacitance thatcauses metamaterial structure 140D-1 to resonate at a specified radiofrequency.

As indicated in FIG. 8, phase shifting element array 100D furtherincludes a base metal structure 120D disposed on upper dielectric layer141D-1 that is spaced (e.g., electrically isolated) from each of metalisland structures 141D-1 to 141D-4 in a manner similar to the singleelement embodiment described above. In this case, base metal structure120D defines four openings 123D-1 to 123D-4, each having an associatedinner peripheral edge that is separated from an outer peripheral edge ofassociated metal island structures 141D-1 to 141D-4 by way of peripheralgaps G1 to G4 (e.g., island structures 141D-1 is disposed in opening123D-1 and is separated from base metal structure 120D by gap G1).Variable capacitors 150D-1 to 150D-4 respectively extend across gaps G1to G4, and have one terminal connected to an associated metal islandstructure 141D-1 to 141D-4, and a second terminal connected to basemetal structure 120D (e.g., variable capacitor 150D-1 extends across gapG1 between metal island structure 141D-1 and base metal structure 120D).Base metal structure 120D and metal island structures 141D-1 to 141D-4are preferably formed by etching a single metal layer (e.g., bothcomprise the same metal composition, e.g., copper).

FIG. 8 also shows phase shifting element array 100D incorporated into aphased array system 300D that includes a signal source 305D and acontrol circuit 310D. Signal source 305D is configured to operate in themanner described above to generate input signal S_(IN) having theresonance radio frequency of metamaterial structures 140D-1 to 140D-4.Control circuit 310D is configured to generate phase control voltagesVc1 to Vc4 that are transmitted to variable capacitors 150D-1 to 150D-4,respectively, by way of metal via structures 145D-1 to 145D-4 in themanner described above, whereby variable capacitors 150D-1 to 150D-4 arecontrolled to apply associated variable capacitances C_(V1) to C_(V4)onto metal island structures 141D-1 to 141D-4, respectively. Accordingto an aspect of the present embodiment, because metamaterial structures140D-1 to 140D-4 are aligned in a one-dimensional array (e.g., in astraight line), variations in output phases p_(OUT1) to p_(OUT4) causeresulting beam B to change direction in a planar region (e.g., in thephase shaped, two-dimensional plane P, which is shown in FIG. 8).

FIG. 9 is simplified top view showing a phased array system 300Eincluding a phase shifting element array 100E having sixteenmetamaterial structures 140E-11 to 140E-44 surrounded by a base metalstructure 120E, a centrally located signal source 305E, and a controlcircuit 310E (which is indicated in block form for illustrativepurposes, but is otherwise disposed below metamaterial structures140E-11 to 140E-44).

According to an aspect of the present embodiment, metamaterialstructures 140E-11 to 140E-44 are disposed in a two-dimensional patternof rows and columns, and each metamaterial structure 140E-11 to 140E-44is individually controllable by way of control voltages V_(C11) toV_(C44), which are generated by control circuit 310E and transmitted byway of conductive structures (depicted by dashed lines) in a mannersimilar to that described above. Specifically, uppermost metamaterialstructures 140E-11, 140E-12, 140E-13 and 140E-14 form an upper row, withmetamaterial structures 140E-21 to 140E-24 forming a second row,metamaterial structures 140E-31 to 140E-34 forming a third row, andmetamaterial structures 140E-41 to 140E-44 forming a lower row.Similarly, leftmost metamaterial structures 140E-11, 140E-21, 140E-31and 140E-41 form a leftmost column controlled by control voltagesV_(C11), V_(C21), V_(C31) and V_(C41), respectively, with metamaterialstructures 140E-12 to 140E-42 forming a second column controlled bycontrol voltages V_(C12) ^(to V) _(C42), metamaterial structures 140E-13to 140E-43 forming a third column controlled by control voltages V_(C13)to V_(C43), and metamaterial structures 140E-14 to 140E-44 forming afourth (rightmost) column controlled by control voltages V_(C14) toV_(C44).

According to an aspect of the present embodiment, two variablecapacitors 150E are connected between each metamaterial structure140E-11 to 140E-44 and base metal structure 120E. The configuration andpurpose of variable capacitors 150E is the same as that provided above,where utilizing two variable capacitors increases the range of variablecapacitance applied to each metamaterial structure. In the illustratedembodiment, a single control voltage is supplied to both variablecapacitors of each metamaterial structure. In addition, a larger numberof variable capacitors may be used.

Control circuit 310E is configured to generate phase control voltagesV_(c11) to V_(c44) that are transmitted to variable capacitors 150E ofeach metamaterial structure 140E-11 to 140E-44, respectively, such thatvariable capacitors 150E are controlled to apply associated variablecapacitances to generate associated output signals having individuallycontrolled output phases. According to an aspect of the presentembodiment, because metamaterial structures 140E-11 to 140E-44 arearranged in a two-dimensional array (e.g., in rows and columns),variations in output phases cause resulting beams to change direction inan area defined by a three-dimensional region, shown in FIGS. 10A to10C. Specifically, FIGS. 10A, 10B and 10C are diagrams depicting theradiation pattern at 0, +40 and −40 degrees beam steer. The radiationpattern consists of a main lobe and side lobes. The side lobes representunwanted radiation in undesired directions.

The system including the metamaterial phased array described herein canbe configured to provide localized heat to a tumor site non-invasively.The output signal at the tumor site (e.g., the target region) can bedynamically controlled with respect to depth control, steering, shape,focus and intensity to provide a predetermined therapeutic heat flux fortreating the tumor. Destructive interference of the component outputsignals of the phased array elements nullifies the EM field at thesurface of the body and other non-targeted areas, thus the temperatureincrease in these regions can be controlled to be negligible.

FIGS. 10D-10G show results of spatial modeling the energy of thebeamformed output signal from the system. FIGS. 10D-10G demonstratefocusing the local hyperthermia beam in x, y, and depth (into the body)dimensions using the metamaterials phased array 1010 as describedherein, where darker shaded regions 1001 of the beam indicate regions ofhigher energy of the output signal and lighter shaded regions 1002 ofthe beam indicate lower energy regions of the output signal.

Some embodiments involve an imaging system as illustrated in thesimplified block diagram of FIG. 11. The illustrated system1100 includesa control system 1163 configured to control the phases and/or amplitudesof the respective component output signals of the elements of the phasedarray 162 resonating at a frequency of an input signal from an inputsource. The phases and/or amplitudes of the phased array elements arecontrolled so that the output signal is caused to scan or “sweep” anarea 1164 a of a patient's body 1164 into which the output signal isdirected. The control circuit 1163 generates scan direction data thatincludes the instantaneous scan direction of the output signal. Thesystem includes a receiver circuit 1165 configured to detect a portionof the output signal that is reflected from one or more structures inthe scan area 164 a interior to the body. A signal processing circuit1166 combines information from the scan direction and the detectedportion of the output signal to provide information related to thepresence and location of the structures.

FIG. 12 is a simplified side view diagram showing an imaging system 1200according to an exemplary embodiment. System 1200 generally includes asignal source 1205, a phase shifting element array 100 and a beamcontrol circuit 1210 for generating a scan beam B that is directed intoa target region F. System 1200 also includes a receiver circuit 1220 forprocessing reflected beam portions B_(R) from target region F, and asignal processing circuit 1230 for processing reflected beam data todetermine presence, position, and/or image information related to a bodystructure O that might be present in area F.

Signal source 1205 is a signal transmission source (e.g., a feed horn ora leaky-wave feed) disposed in close proximity to phase shifting elementarray 100, and is configured to generate a radio wave frequency inputsignal S_(IN) at a particular radio wave frequency (e.g., in the rangeof 3 kHz to 300 GHz) and an input phase p_(IN). As previously discussed,the radio wave frequency of input signal S_(IN) is generated to matchresonance characteristics of phase shifting element array 100.

According to the exemplary embodiment, phase shifting element array 100includes four metamaterial structures 140-1 to 140-4, each configured toresonate at the radio wave frequency of input signal S_(IN) such thatphase shifting element array 100 generates four output signals S_(OUT1)to S_(OUT4), each having the radio wave frequency and an associatedoutput phase p_(OUT1) to p_(OUT4). For example, when metamaterialstructure 140-1 is configured to resonate at 2.4 GHz and input signalS_(IN) is generated at 2.4 GHz, metamaterial structure 140-1 generatesoutput signal S_(OUT1) at 2.4 GHz by retransmitting (e.g.,reflecting/scattering) input signal S_(IN). When all four metamaterialstructures 140-1 to 140-4 are configured in this manner and subjected toinput signal S_(IN), array 100 produces four separate output signalsS_(OUT1) to S_(OUT4,) each having a frequency of 2.4 GHz. According to apresently preferred embodiment, metamaterial structures 140-1 to 140-4may be layered metal-dielectric composite architectures, as describedwith reference to FIGS. 3-5, but may be engineered in a different form,provided the resulting structure is configured to resonate at the radiofrequency of applied input signal S_(IN), and has a large phase swingnear resonance. In providing this resonance characteristic, metamaterialstructures 140-1 to 140-4 are produced with associated inherent “fixed”capacitances C_(M1) to C_(M4) and associated inductances thatcollectively provide the desired resonance characteristics. Asunderstood in the art, the term “metamaterial” identifies anartificially engineered structure formed by two or more materials andmultiple elements that collectively generate desired electromagneticproperties, where metamaterial achieves the desired properties not fromits composition, but from the exactingly-designed configuration (e.g.,the precise shape, geometry, size, orientation and arrangement) of thestructural elements formed by the materials. As used herein, the phrase“metamaterial structure” is intended to mean a dynamicallyreconfigurable/tunable metamaterial and large phase swing propertiessuitable for the purpose set forth herein. Metamaterial structuresachieve their desired effects by incorporating structural elements ofsub-wavelength sizes, e.g. features that are actually smaller than theradio frequency wavelength of the waves they affect. Although fourmetamaterial structures are utilized in the exemplary embodiment, thisnumber is arbitrarily selected for illustrative purposes and brevity,and array 100 may be alternatively produced with any number ofmetamaterial structures.

According to another aspect, beam control circuit 1230 comprisesintegrated circuitry configured to generate and apply four variablecapacitances C_(V1) to C_(V4) onto metamaterial structures 140-1 to140-4, respectively, such that an effective capacitance of eachmetamaterial structure is altered by a corresponding change in theapplied variable capacitance C_(V1). As mentioned above, eachmetamaterial structure 140-1 to 140-4 is produced with associatedinherent “fixed” (unchanging) capacitances C_(M1) to C_(M4),respectively. The effective capacitance of each metamaterial structure140-1 to 140-4 is generated by a product of the structure's inherent(fixed) capacitance and an associated applied variable capacitance. Forexample, metamaterial structure 140-1 has an effective (operating)capacitance C_(eff1) generated by inherent (fixed) capacitance C_(M1)and associated variable capacitance C_(V1), which is applied ontometamaterial structure 140-1 by beam control circuit 130 usingtechniques described below. Similarly, metamaterial structure 140-2 hasan effective (operating) capacitance C_(eff2) generated by inherentcapacitance C_(M2) and associated applied variable capacitance C_(V2),metamaterial structure 140-3 has an effective (operating) capacitanceC_(eff3) generated by inherent capacitance C_(M3) and associated appliedvariable capacitance C_(V3), and metamaterial structure 140-4 has aneffective (operating) capacitance C_(eff4) generated by inherentcapacitance C_(M4) and associated applied variable capacitance C_(V4).Some embodiments achieve control over output phase p_(OUT1) to p_(OUT4)of radio frequency (output) signals S_(OUT1) to S_(OUT4) without the useof conventional phase shifters simply by controlling variablecapacitances C_(V1) to C_(V4) applied to metamaterial structures 140-1to 140-4.

According to another aspect, beam control circuit 310 is furtherconfigured to coordinate and vary (e.g., change over time) variablecapacitances C_(V1) to C_(V4) applied to metamaterial structures 140-1to 140-4 such that beam B (generated by way of output signals S_(OUT1)to S_(OUT4), collectively) scans, or “sweeps”, across target region F ata predetermined rate over a predetermined scan range (pattern). That is,at each instant a particular set of variable capacitances C_(V1) toC_(V4) are applied to metamaterial structures 140-1 to 140-4 such thatoutput signals S_(OUT1) to S_(OUT4) have correspondingly differentoutput phases p_(OUT1) to p_(OUT4) (e.g., output signal S_(OUT1) isgenerated at output phase p_(OUT1) that is different from output phasep_(OUT1) of output signal S_(OUT2)), and output phases p_(OUT1) top_(OUT4) are coordinated such that output signals S_(OUT1) to S_(OUT4)cumulatively emit scan beam B in a direction determined by theinstantaneous set of output phase values. At the beginning of each scanpass, the output phases p_(OUT1) to p_(OUT4) are coordinated such thatbeam B is directed along an initial direction (e.g., a scan angle of−60°, corresponding to a leftmost beam angle). As understood in the art,by coordinating output phases p_(OUT1) to p_(OUT4) in this way, thecombined electro-magnetic wave generated by output signals S_(OUT1) toS_(OUT4) is reinforced in a particular “desired” direction, andsuppressed in undesired directions, whereby the scan beam B is emittedat a desired angle from the front of array 100. Output phases p_(OUT1)to p_(OUT4) are subsequently varied such that beam B begins sweepingfrom the initial direction toward a central direction (e.g., directly infront of array 100, and corresponding to a scan angle of 0°), and thencontinues to sweep from the central direction to an ending direction(e.g., a scan angle of +60°, corresponding to a rightmost beam angle).The scan rate and repeat/refresh rate at which beam B is generated isdetermined by the rate at which output phases p_(OUT1) to p_(OUT4) arevaried. Beam control circuit 1210 generates these output phases p_(OUT1)to p_(OUT4) changes by changing the variable capacitances C_(V1) toC_(V4) applied to metamaterial structures 140-1 to 140-4 over time(e.g., in accordance with predefined time-based functions), whereby beamcontrol circuit 1210 causes beam B to scan (sweep) across target field Fin a characteristic “radar-like” sweep pattern.

According to some embodiments, beam control circuit 1210 is implementedusing variable capacitors (varicaps) 150-1 to 150-4 and a phase controlcircuit 1215, where variable capacitors 150-1 to 150-4 are respectivelycoupled to metamaterial structures 140-1 to 140-4, and are controlled byway of phase control voltages Vc1 to Vc4 generated by phase controlcircuit 1215 (e.g., variable capacitor 150-1 generates variablecapacitance C_(V1) having a capacitance level that is proportional tothe voltage level of phase control voltage Vc1). As understood in theart, variable capacitors are typically two-terminal electronic devicesconfigured to produce a capacitance that is intentionally and repeatedlychangeable by way of an applied electronic control signal. In this case,variable capacitors 150-1 to 150-4 are coupled to metamaterialstructures 140-1 to 140-4 such that respective effective capacitancesC_(eff1) to C_(eff4) of metamaterial structures 140-1 to 140-4 aredetermined by a product of inherent capacitance C_(M1) to C_(M4) andvariable capacitances C_(V1) to C_(V4) supplied by variable capacitors150-1 to 150-4. For example, effective capacitance C_(eff1) ofmetamaterial structure 140-1 is determined by inherent capacitanceC_(M1) and variable capacitance C_(V1), which is supplied tometamaterial structure 140-1 during operation by variable capacitor150-1. Because output phase p_(OUT1) is determined in part by effectivecapacitance C_(eff1), output signal S_(OUT1) is “tunable” (adjustablycontrollable) to a desired phase value by way of changing variablecapacitance C_(V1), and this is achieved by way of changing the phasecontrol signal Vc1 applied to variable capacitor 150-1.

Phase control voltages Vc1 to Vc4 are applied across variable capacitors150-1 to 150-4 such that each variable capacitance C_(V1) to C_(V4) isapplied to metamaterial structures 140-1 to 140-4, respectively. Forexample, variable capacitor 150-1 includes a first terminal 151connected to metamaterial structure 140-1 and a second terminal 152connected to ground, whereby variable capacitor 150-1 generatesassociated variable capacitance C_(V1) having a capacitance level thatvaries in accordance with the voltage level of phase control voltage Vc1in the manner illustrated in FIG. 2 (e.g., the capacitance level ofvariable capacitance C_(V1) changes in direct proportion to phasecontrol voltage Vc1). As indicated in FIG. 1, variable capacitors 150-2to 150-4 are similarly connected, and share a common voltage source(e.g., ground) with variable capacitor 150-1. In an alternativeembodiment, the conductive structures that transmit phase controlvoltages Vc1 to Vc4 from phase control circuit 1215 are either connectedto metamaterial structures 140-1 to 140-4, which in turn are connectedto associated variable capacitors 150-1 to 150-4.

Imaging system 1200 further includes a receiver 1220 and signalprocessing circuitry 1230 that are utilized to detecting body structuresin target region F, and to generate target location data that can beutilized, for example. In the exemplary embodiment, phase controlcircuit 1215 is configured to generate beam direction data D_(BD)indicating an instantaneous beam direction θ of said scan beam B as itsweeps the target region F, and receiver circuitry 1220 is configured todetect portions B_(R) of the scan beam B that are reflected from bodystructures, e.g., tumors disposed in the target region F. Receivercircuitry 1220 also generates beam detection data D_(BR) indicating eachtime a reflected beam portion B_(R) is detected. Signal processingcircuitry 1230 is configured to determine the position of each structureO in target region F by correlating beam detection data D_(BR) receivedfrom receiver circuitry 1220 with beam direction data D_(BD) receivedfrom beam control circuit 310 at the time of beam portion detection. Forexample, assume the body structure of interest O is disposed a positioncorresponding to a −45° direction angle relative to array 100. In thiscase, as beam B sweeps across field F and passes the −45° directionangle, receiver circuitry 1220 generates beam detection data D_(BR)indicating the reception of reflected beam portion B_(R) caused by thepresence of structure O, and then signal processing circuitry 1230correlates the reception of this reflected beam portion B_(R) with beamdirection data D_(BD) (e.g., indicating that beam B was directed at −45°when the reflected beam portion was received) to determine the positionof structure O. Signal processing circuitry 1230 also optional circuitryfor generating other useful information (e.g., providing an image of thebody structure, determining the size of the body structure O and/orposition of the body structure O with respect to the array 100 or otherreference points using known signal processing techniques.

Embodiments described herein involve a therapy and/or imaging systemthat uses a phase shifting array including a plurality of metamaterialstructures that resonate in response to an input electromagnetic (EM)signal. The phase shifting array generates an output EM signal that is asum of component output electromagnetic signals generated respectivelyby the metamaterial structures and is configured to propagate wirelesslythrough at least a portion of a patient's body. A control circuitcontrols one or both of phases and amplitudes of the componentelectromagnetic output signals so that at least one of constructive anddestructive interference between the component output electromagneticsignals causes the output signal to have a higher intensity EM radiationat a target region interior to the body and to have a zero or lowintensity radiation at a non-target region interior to the body. Thecontrol circuit is configured to control at least one of position,focus, and intensity of the higher intensity EM radiation at the targetregion. The higher intensity EM radiation is capable of generating aheat flux suitable to provide hyperthermia therapy at the target region.For example, the EM radiation in the target region may provide a tissuetemperature in a range of about 40 C to about 60 C.

The control circuit includes variable capacitors electrically coupledrespectively to the metamaterial structures so that a change incapacitance of one of the variable capacitors changes a phase of acomponent output signal of an associated metamaterial structure. Acontrol signal generator provides control signals that controlcapacitances of the variable capacitors. The EM signal propagateswirelessly to the array of metamaterial structures through a wire probeantenna, e.g., through a wire probe antenna and/or a waveguide. Eachmetamaterial structure include a first metal layer structure, anelectrically isolated second metal layer structure, and a dielectriclayer disposed between the first and second metal structures. The firstand second metal layer structures are cooperatively configured such thatthe metamaterial structure resonates at a frequency of the input EMsignal at a fixed capacitance. In some embodiments, the first metallayer structure is disposed on an upper dielectric surface of thedielectric layer, and a third metal layer structure is disposed on theupper dielectric surface and spaced apart from the first metal layerstructure. A variable capacitor of the control circuit has a firstterminal electrically coupled to the first metal layer structure and asecond terminal electrically coupled to the third metal layer structure.

In some embodiments, system involves a body imaging system wherein thecontrol signal is configured to control the component EM output signalsto scan the output signal across the target region. In this embodiment,the control circuit can also be configured to generate beam directiondata indicating instantaneous scan direction of the output signal. Theimaging system includes a receiver circuit configured to detect aportion of the output signal reflected from structures interior to thebody. A signal processing circuit processes the scan direction and thereflected portion of the output signal and to provide information aboutthe structures, wherein the information may include location and/orimage information.

As used herein, directional terms such as “upper”, “upward”,“uppermost”, “lower”, “lowermost”, “front”, “rightmost” and “leftmost”,are intended to provide relative positions for purposes of description,and are not intended to designate an absolute frame of reference. Inaddition, the phrases “integrally formed” and “integrally connected” areused herein to describe the connective relationship between two portionsof a single fabricated or machined structure, and are distinguished fromthe terms “connected” or “coupled” (without the modifier “integrally”),which indicates two separate structures that are joined by way of, forexample, adhesive, fastener, clip, or movable joint.

The foregoing description of various embodiments has been presented forthe purposes of illustration and description and not limitation. Theembodiments disclosed are not intended to be exhaustive or to limit thepossible implementations to the embodiments disclosed. Manymodifications and variations are possible in light of the aboveteaching.

1. A device comprising: a phase shifting element array including aplurality of metamaterial structures that resonate in response to aninput electromagnetic (EM) signal, the phase shifting element arraygenerating an output EM signal that is a sum of component outputelectromagnetic signals generated respectively by the metamaterialstructures and is configured to propagate wirelessly through at least aportion of a patient's body; and a control circuit configured to controlone or both of phases and amplitudes of the component electromagneticoutput signals so that at least one of constructive and destructiveinterference between the component output electromagnetic signals causesthe output signal to have a higher intensity EM radiation at a targetregion interior to the body and to have a zero or low intensityradiation at a non-target region interior to the body.
 2. The device ofclaim 1, wherein the higher intensity electromagnetic radiationgenerates a tissue temperature suitable for hyperthermia therapy at thetarget region.
 3. The device of claim 2, wherein the tissue temperatureat the target region is in range of about 40 C to 50 C.
 4. The device ofclaim 2, wherein the control circuit is configured to control at leastone of position, focus, and intensity of the higher intensity EMradiation at the target region.
 5. The device of claim 1, wherein thecontrol circuit comprises: variable capacitors electrically coupledrespectively to the metamaterial structures so that a change incapacitance of one of the variable capacitors changes a phase of acomponent output signal of an associated metamaterial structure; and acontrol signal generator configured to generate control signals thatcontrol capacitances of the variable capacitors.
 6. The device of claim1, wherein the input EM signal is propagated wirelessly to the array ofmetamaterial structures through a wire probe antenna.
 7. The device ofclaim 1, wherein the input EM signal is propagated to the array ofmetamaterial structures though a waveguide.
 8. The device of claim 1,wherein each metamaterial structure comprises: a first metal layerstructure; an electrically isolated second metal layer structure; and adielectric layer disposed between the first and second metal structures,wherein the first and second metal layer structures are cooperativelyconfigured such that the metamaterial structure resonates at a frequencyof the input EM signal at a fixed capacitance.
 9. The device of claim 8,wherein: the first metal layer structure is disposed on an upperdielectric surface of the dielectric layer; the metamaterial structurefurther comprises a third metal layer structure disposed on the upperdielectric surface and spaced apart from the first metal layerstructure; and a variable capacitor has a first terminal electricallycoupled to the first metal layer structure and a second terminalelectrically coupled to the third metal layer structure.
 10. The deviceof claim 8, wherein: the first metal layer structure is disposed on anupper dielectric surface of the dielectric layer; the metamaterialstructure further comprises a third metal layer structure disposed onthe upper dielectric surface and spaced apart from the first metal layerstructure; a second metamaterial structure further comprises a fourthmetal layer structure disposed on the lower dielectric surface andspaced apart from the second metal layer structure; and a variablecapacitor has a first terminal electrically coupled to the second metallayer structure and a second terminal electrically coupled to the fourthmetal layer structure.
 11. The device of claim 10, wherein themetamaterials structure on the upper dielectric surface is a mirrorimage of the metamaterial structure on the lower dielectric surface. 12.The device of claim 8, wherein the first metal layer structure comprisesa patterned planar structure defining one or more open regions.
 13. Thedevice of claim 12, wherein the first metal layer structure comprises: aperipheral frame portion including an outer peripheral edge; one or moreradial arms, each radial arm having a first end integrally connected tothe peripheral frame portion and extending inward from the peripheralframe portion toward a central region of the metamaterial structure; andan inner structure integrally connected to second ends of the one ormore radial arms, the inner structure being spaced from the peripheralframe portion.
 14. The device of claim 1, wherein the control signal isconfigured to control the component EM output signals to scan the outputsignal across a detection area.
 15. The device of claim 14, wherein: thecontrol circuit is configured to generate beam direction data indicatinginstantaneous scan direction of the output signal; and furthercomprising: a detector circuit configured to detect a portion of theoutput signal reflected from a structure interior to the body; and asignal processing circuit configured to combine the scan direction andthe reflected portion of the output signal and to provide informationabout the structure.
 16. The device of claim 15, wherein the informationcomprises one or more of presence, size, location, and imageinformation.
 17. A method comprising: generating an output EM signalthat is a sum of component output electromagnetic signals generatedrespectively by a plurality of metamaterial structures that resonate inresponse to an input electromagnetic (EM) signal; propagating the outputEM wirelessly through at least a portion of a patient's body; andcontrolling one or both of phases and amplitudes of the componentelectromagnetic output signals so that at least one of constructive anddestructive interference between the component output electromagneticsignals causes the output signal to have a higher intensity EM radiationat a target region interior to the body and to have a zero or lowintensity radiation at a non-target region interior to the body.
 18. Themethod of claim 17, wherein the higher intensity electromagneticradiation generates a tissue temperature suitable for hyperthermiatherapy at the target region.
 19. The method of claim 17,wherein:controlling the component electromagnetic output signals comprisescontrolling the component electromagnetic output signals to scan theoutput signal across a detection area; generating beam direction dataindicating instantaneous scan direction of the output signal; detectinga portion of the output signal reflected from a structure interior tothe body; and combining the scan direction and the reflected portion ofthe output signal and to provide information about the structure.
 20. Adevice comprising: a phase shifting element array including a pluralityof metamaterial structures that resonate in response to an inputelectromagnetic (EM) signal, the phase shifting element array generatingan output EM signal that is a sum of component output electromagneticsignals generated respectively by the metamaterial structures and isconfigured to propagate wirelessly through at least a portion of apatient's body; and a control circuit configured to control one or bothof phases and amplitudes of the component electromagnetic output signalsso that at least one of constructive and destructive interferencebetween the component output electromagnetic signals causes the outputsignal to scan the output signal across a detection area; and generatebeam direction data indicating instantaneous scan direction of theoutput signal; a detector circuit configured to detect a portion of theoutput signal reflected from a structure interior to the body; and asignal processing circuit configured to combine the scan direction andthe reflected portion of the output signal and to provide informationabout the structure.